There's another thing you could try (has nothing to do with texture caching for final rendering, but can help if you're short on RAM and your textures are large): Poser 7 allows you to adjust the texture preview size. Regardless of the actual size of the texture, the maximum resolution Poser 7 will load it at for previewing a scene is specified on the Preview tab of the Render Settings dialog. So lowering that value will leave more room for other data while posing, animating, etc.